402 OCCURRENCE OF COAL, 



observable in the sand-stone, being an ochreous stain, extending to a certain 

 distance, but strongest in the immediate contact of the vein. In one loca- 

 lity, a saline efflorescence accompanies it, as also, sulphurous incrustations. 

 Specimens have been obtained from another locality, with disseminated 

 pyrites. 



The specific gravity varies from 1. 32. to 1. 58. The latter being 

 too high from adhering stand-stone. The hardness rather exceeds that of 

 Selenite : 2. 0. to 2. 5. of Mohs' system, may represent the limits : it is of a 

 jet black color, possesses considerable lustre, particularly the smaller veins, 

 which are extremely beautiful. The composition is, in general, impalpable, 

 but it has sometimes the ligneous structure — in the latter case, the lustre is 

 low in the direction of the fibres, and the fracture less like that of true 

 Coal. The transverse fracture has, however, the usual lustre, and when 

 reduced to fragments, it is not distinguishable from the other kinds. Where 

 the ligneous fibre has disappeared, the fracture is perfect conchoidal, and 

 uneven, the former being frequently marked with concentric circles, similar 

 to what is observed in Cannel Coal. The fragments are indeterminately 

 angular, approaching to wedge-shaped. It burns with flame, giving out a 

 thick smoke and bituminous smell, which, in some specimens, is accompanied 

 by the odor of sulphurous acid. It leaves a reddish brown ash, of equal 

 bulk with the original fragment. 



This general account of its properties, enables us to refer it at 

 once to the Bituminous Coal of Mohs. The specific gravity, in some of the 

 specimens, is a little higher, but this is obviously the effect of impurities. 

 It is more difficult to discover, with which of the numerous sub-species and 

 kinds of former writers, it is synonimous. The descriptions are so vague, 

 and there is so much similarity in the few particulars that approach to defi- 

 niteness, that one cannot but consider the greater part of them as merely 



